Stabilizing print-out material



United States Patent P 3,501,299 STABILIZING PRINT-OUT MATERIAL Henry W. Pestalozzi, Binghamton, N.Y., assignor to GAF Corporation, New York, N.Y., a corporation of Delaware No Drawing. Filed Mar. 17, 1967, Ser. No. 623,802 Int. Cl. G03c 1/34, 1/86 U.S. C]. 9685 4 Claims ABSTRACT OF THE DISCLOSURE This invention is directed to print-out materials carrying a silver halide emulsion in which a latent image formed by the high intensity pattern produced by an oscillograph is photolytically developed by a prolonged exposure to light of low intensity. The formation of fog which is normally formed during storage or upon prolonged exposure to light is avoided by placing a colloid layer containing lead bromide between the support and the print-out layer. The images can be made permanent by development and fixing, the presence of the lead bromide in the undercoating again prevents the formation of fog.

The present invention relates, in general, to light-sensitive silver halide systems which form a print-out image and particularly to certain gelatin undercoatings for stabilizing print-out materials.

Light-sensitive silver halide systems may be divided into three main groups or classes; namely those which are developed by chemical treatment after exposure, those which contain an excess of silver salts to form a print-out image and those which are developed by a prolonged second exposure to actinic light.

The present invention is concerned, especially, with the last of these groups; namely, print-out materials which are photolytically developed, Ordinarily, print-out emulsions of this type consist of silver chloride, bromo-iodide suspensions in a gelatin binder to which divalent metal salts, such as tin chloride, lead bromide and lead iodide, or cadmium chloride can be added. Many such emulsions are presently available from various manufacturers under various trade names such as Du Ponts Linowrit, Eastman Kodaks Linagraph and GAFs Anscotrace papers. It has been found out by previous investigations that the presence of silver iodide in the emulsion, preferably on the grain surface, is beneficial in the type of print-out silver halide emulsions which are photolytically developed. This can be accomplished by incorporating lead iodide into the emulsion. However, the presence of lead iodide imparts an intense yellow color to the emulsion which subsequently slowly turns brown upon exposure as iodine is liberated. Attempts to avoid discoloration led to the use of other lead halides, such as lead bromide, which do not produce these color side effects. However, such materials are generally unsatisfactory due to a lack of storage stability and a lack of versatility under a wide range of exposure and development conditions. Moreover, ripened silver halide emulsions containing lead bromide and an alkali halide normally produce a reversal print-out image rendering them unsuitable for producing negative print-out work.

It is, therefore, a primary object of this invention to produce a print-out material which is stable and not subject to discoloration.

Yet another object of this invention resides in the provision of a novel print-out material in which the image formed by photolytic development can subsequently be rendered permanent by conventional chemical development.

Other objects and advantages of the invention will be apparent from the following description.

3,501,299 Patented Mar. 17, 1970 The above objects are achieved by providing a photographic element comprising in the following order a support coated with a first layer containing lead bromide dispersed in a suitable binder or carrier material and a second layer of a silver halide emulsion.

The lead bromide undercoating must be applied prior to the emulsion coating and is prepared from a suspension of lead bromide in a colloid carrier material such as gelatin or gelatin derivatives, for instance acylated gelatin products.

The optimum amount of lead bromide in the undercoating may vary with different silver halide emulsions and depends somewhat on the quantities of emulsion adjuvants such as chemical and optical sensitizers used. Beneficial amounts of lead bromide in the colloid undercoating for use with negative print-out materials range from about 15 to 250 grams per square meter of coated area. The thickness of the undercoating may vary from 5 to 15 microns.

The type of support employed may be varied and depends to a certain extent on the final use of the product. Ordinarily, photographic papers of the type commonly employed for photolytic print-out recordings are quite satisfactory, although film base supports such as cellulose esters or polyesters may also be used. The sensitivity of the emulsions made according to the present invention is quite satisfactory, being fully comparable to that of other photolytic print-out recording materials. However, the finished prints are distinguished by a substantially superior image stability, a properly not possessed by the photolytic print-out recording media of the prior art.

According to the present invention, a photographic emulsion is prepared which is suitable for recording high intensity illumination and subsequent development by exposure to actinic light of lower intensity. The emulsion is made up in the usual manner. Gelatin is dissolved in water, after which the silver halide-forming ingredients are added, preferably by the so-called double-jet technique. The reagents chosen are of the quality necessary to produce essentially pure grains of silver bromide. Thus, an aqueous solution of an alkali metal bromide, e.g., sodium or potassium bromide, is added simultaneously with the silver nitrate solution. Both of these reactants are introduced by adjustable jets as is well known in the art, to control their proportions for essentially complete reaction. This procedure is carefully adjusted to assure the formation of essentially pure silver bromide grain in the emulsion.

The next step involves adding a small proportion of iodide ions, e.g., sodium, potassium or lithium iodide preferably, the amounts ranging from 0.2 to 10 mole percent based on the amount of silver.

Ripened emulsions containing from 3 to 7 mole percent of lead bromide and 6 mole percent of potassium iodide produce a reversal print-out image. However, if the emulsion layer is coated on a base carrying a lower layer containing lead bromide dispersed in gelatin, then an excellent negative print-out image is obtained. Moreover, if the potassium iodide content of the emulsion is reduced to 1.0 mole percent, the net density and stability are further improved.

There appears to be a direct relation between the eifect of the lead bromide undercoat and that of the potassium iodide and lead bromide content of the emulsion. Results indicate that the undercoat containing the lead bromide improves the net negative trace density in the ripened emulsions, whereas in the unripened emulsions the effect is most pronounced with emulsions of low potassium iodide and lead bromide concentrations.

For the negative print-out type of operation, both ripened and unripened emulsions can be employed. In ripened emulsions, the proportions of silver iodide should subbed cellulose acetate filmbase, resulting in a coating weight of 19 grams of lead bromide per square meter. The silver halide emulsion applied to the undercoating was the one describedin Example 1.

'"One sample ofthis material'was compared with an essentially identical material which differed to the extent 3 that it did nothave a gelatin lead bromide undercoating.

The dried samples were exposed to 5640 lux. sec. at

"10. seconds in an Edgerton-Germeshausen and Grier SensitdmeterMlcVI and post-exposed under a 375 watt photofiood at a distance-of 50 cm. through a yellow filter -foil transmitting beyond 520 mg. The post-exposed film -Thefollowing'examples will serve to illustrate the practice of the invention:

. EXAMPLE .1 v p A baryta papersupport was coated with a lead bromide undercoat layer whichhad been prepared by dispersing'183 grams oflead bromide in 1 liter ofa 10% gelatin solution with 'thorough'stirring: This lead bromide undercoating was coated to athickness of'about15 microns, corresponding to about 240 grams of lead bromide per squaremeter. This undercoating'was dried and overcoatedwith a. photolytic print-out silver halide emulsion. This emulsion, which consisted originally.

of pure silver bromide,-was produced by the double-jet mixing of 0.5 rnoleofpotassium bromide and 0.5 mole of silver nitrate in a solution of 20.0 grams of inert gelatin and 0.6'gramof potassium bromide (lmole percent) in 480 ml.of water at'65" C.- The emulsion was then precipitated with a polystyrenesulfonate solution, washed and reconstituted; then 0.5 mole percent of potassium iodide, based onthe silver content, was added with stirring. After about minutes of continued stirring, mole percent of lead bromide, based on silver, was added as anaqueous slurry. This material was then coated onto the baryta'paper carrying the lead bromide undercoating. The coated and dried material was exposed to a high intensity pattern produced by 'anoscillograph. The

oscillograph trace was thendeveloped by exposure to fluorescent light of moderately low intensity. A clear, strong image of the "oscilloscope pattern was obtained and the finished sheet had good shelf life; The negativeirnage remained visible without excessive darkeningof.

the background for a substantial length of time under 'ordi: nary oflice storage conditions.

In one set of samples, the post-exposed image was permitted, i.e., stabilized against further exposure to light by treating it in a commercial developer solution known as Ansco A-47 which has the following composition:

Grams. Metol 1.5 Sodium sulfite, anhydrous 45.0 Sodium bisulfite -1 .1.0 Hydroquinone 3.0 Sodium carbonate, monohydrated 6.0 Potassium bromide .8

Water to make 1.0 liter.

to ambient light of low intensity, resulting in an image.

EXAMPLE 2 Example 1 was repeated with the following changes. The gelatin undercoat' was prepared by dissolving at a temperature of 40? C. 100 grams-of dry gelatin in a solution of 15 grams of lead bromide (PbBrin 1 liter of water. This solution was applied as an undercoat to a -was permanized by treatment in the following developer:

Grams Metol 2.5 Ascorbic acid 10.0 KBr. 1.0

Na-metaborate 35.0 P1 0 to makell) liter The timeof"'developrrient'was 3 minutes at 20 C.,

: after which the stripswere immersed for 1 minute in an acid stop bath' and fixed for'3 minutes in Liquafix.

.Thetdeveloped prints'were' stopped in a dilute solution of acetic acid and fixed in a hypo solution.

The following results were obtained:

Density Image Fog 0 minutes: I

a 3. 55 91 1. 26 10 minutes:

an; 3.61 1.20 b 1. 16 l0 a=without lead bromide undereoat. b =with lead bromide undercoat.

' What is claimed is:

1. A photographic element comprising a support having coated thereon a lower layer comprising gelatin and lead bromide, and a photolytic print-out silver halide emulsion layer coated on said lower layer.

2. The photographic element of claim 1, wherein the emulsion comprises gelatin containing essentially pure grains of silver bromide and a small proportion'not in excess of 10 mole percent iodide based on the silver content and from 1 to 10 percent of lead bromidebased on the silver content.

: 3. A photographic element according to claim 2 where} in the support is paper and wherein the lower gelatin layer.-

contains from 1 to 20 weight percent of lead bromide based on the weight of dry gelatin.

4. A photographicelement according to claim 1, where-E in the lead bromide content in the gelatin layer ranges from 15 to 250 grams per square meter of coated area.

References Cited UNITED STATES PATENTS 3,050,391 8/1962 Thompson et al. 9694 XR 3,220,841 11/1965 Stevens 9687 XR NORMAN G. TORCHIN, Primary Examiner EDWARD KIMLIN, Assistant Examiner US. Cl. X.R. 96-110 

